Eugenia Villaverde-de-Sáa

In-sample acetylation-non-porous membrane-assisted liquid–liquid extraction for the determination of parabens and triclosan in water samples

A procedure for the determination of seven parabens (esters of 4-hydroxybenzoic acid), including the distinction between branched and linear isomers of propyl- and butyl-parabens and triclosan in water samples, was developed and evaluated. The procedure includes in-sample acetylation-non-porous membrane-assisted liquid–liquid extraction and large volume injection–gas chromatography–ion trap–tandem mass spectrometry. Different derivatisation strategies were considered, i.e. post-extraction silylation with N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide and in situ acylation with acetic anhydride (Ac2O) and isobutylchloroformate. Moreover, acceptor solvent and the basic catalyser of the acylation reaction were investigated. Thus, in situ derivatisation with Ac2O and potassium hydrogenphosphate (as basic catalyser) was selected. Potassium hydrogenphosphate overcomes some drawbacks of other basic catalysers, e.g. toxicity and bubble formation, while leads to higher responses. Subsequently, other experimental variables affecting derivatisation–extraction yield such as pre-stirring time, salt addition and volume of Ac2O were optimised by an experimental design approach. Under optimised conditions, the proposed method achieved detection limits from 0.1 to 1.4xa0ngxa0L−1 for a sample volume of 18xa0mL and extraction efficiencies, estimated by comparison with liquid–liquid extraction, between 46% (for methyl- and ethyl-parabens) and 110% (for benzylparaben). The reported sample preparation approach is free of matrix effects for parabens but affected for triclosan with a reduction of ≈ 40% when wastewater samples are analysed; therefore, both internal and external calibration can be used as quantification techniques for parabens, but internal standard calibration is mandatory for triclosan. The application of the method to real samples revealed the presence of these compounds in raw wastewater at concentrations up to 26xa0ngxa0mL−1, the prevalence of the linear isomer of propylparaben (n-PrP), and the coexistence of the two isomers of butylparaben (i-BuP and n-BuP) at similar levels.

Determination of perfluorinated compounds in mollusks by matrix solid-phase dispersion and liquid chromatography–tandem mass spectrometry

Perfluorinated compounds (PFCs) have been used for over 40xa0years in different commercial and industrial applications mainly as surfactants and surface protectors and have become an important class of marine emerging pollutants. This study presents the development and validation of a new analytical method to determine the simultaneous presence of eight PFCs in different kinds of mollusks using matrix solid-phase dispersion (MSPD) followed by liquid chromatography–tandem mass spectrometry (LC-MS/MS). Simplicity of the analytical procedure, low volume of solvent and quantity of sample required, low global price, and integration of extraction and clean-up into a single step, are the most important advantages of the developed methodology. Solvent, solid support (dispersing agent), clean-up sorbent, and their amounts were optimized by means of an experimental design. In the final method, 0.5xa0g of sample are dispersed with 0.2xa0g of diatomaceous earth and transferred into a polypropylene syringe containing 4xa0g of silica as clean-up sorbent. Then, analytes are eluted with 20xa0mL of acetonitrile. The extract is finally concentrated to a final volume of 0.5xa0mL in methanol, avoiding extract dryness in order to prevent evaporation losses and injected in the LC-MS/MS. The combination of this MSPD protocol with LC-MS/MS afforded detection limits from 0.05 to 0.3xa0ngxa0g−1. Also, a good linearity was established for the eight PFCs in the range from limit of quantification (LOQ) to 500xa0ngxa0mL−1 with R2u2009>u20090.9917. The recovery of the method was studied with three types of spiked mollusk and was in the 64–126% range. Moreover, a mussel sample was spiked and aged for more than 1xa0month and analyzed by the developed method and a reference method, ion-pair extraction, for comparison, producing both methods statistically equal concentration values. The method was finally applied to the determination of PFCs in different kinds of mollusks revealing concentrations up to 8.3xa0ngxa0g−1 for perfluoroundecanoic acid.

Determination of benzodiazepines, related pharmaceuticals and metabolites in water by solid-phase extraction and liquid-chromatography-tandem mass spectrometry

This work presents a method for the simultaneous determination of 23 benzodiazepines, metabolites and related pharmaceuticals (zolpidem, methylphenidate and ritalinic acid) by solid-phase extraction (SPE) followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Different SPE cartridges were considered: hydrophilic modified reversed-phase (Oasis HLB) and their modified versions containing also a cationic-exchange group (Oasis MCX) or anionic-exchange (Oasis MAX) funcionalities. Stability of analytes and the impact of the final eluate volume on the matrix effects on LC-MS/MS were also considered. In the final method, 100-200 mL of sample are extracted with Oasis MCX (60 mg), eluted with 5 mL of methanol (1.25% NH3) and the eluate concentrated and analyzed by LC-MS/MS. Under these conditions, LOQs were established between 0.1 and 18 ng L(-1) for influent wastewater. The use of surrogated deuterated internal standards allows obtaining recoveries in the 84-122% range. Finally the method was applied to determinate the analytes in wastewater and surface water and 10 compounds were detected in the range of 0.5-170 ng L(-1), being the ritalinic acid (the main metabolite of methylphenidate) the analyte detected in the highest concentrations.

Matrix solid-phase dispersion combined with gas chromatography–mass spectrometry for the determination of fifteen halogenated flame retardants in mollusks

This study presents the development and validation of a new analytical method for the simultaneous determination of fifteen analytes classified as halogenated flame retardants (HFRs) - nine brominated diphenyl ethers (BDEs) and six novel HFRs - in different kinds of mollusks using matrix solid-phase dispersion (MSPD) followed by gas chromatography coupled to negative chemical ionization-mass spectrometry (GC-NCI-MS). The proposed method is the first one developed for such a broad range of HFRs in aquatic biota, featuring several advantages, including low solvent and sample intake, simplicity of operation, reduced cost and integration of extraction and clean-up into a single step. Under optimal conditions, 0.5g of freeze-dried sample, 0.5g of a primary-secondary amine (PSA) as solid support, a sorbent combination of 1.75g of florisil (deactivated with 5% Milli-Q water), 1.75g of acidified silica (10% (w/w) H2SO4) and 0.5g of silica, and 10mL dichloromethane as elution solvent were used. Standard addition over the extract was required however for the correct quantification due to matrix effects in the GC system, particularly for novel HFRs, that could not be compensated with the internal standards. The method afforded LODs in the range of 0.003-0.07ngg(-1) dry weight (0.0006-0.014ngg(-1) on a wet weight basis, assuming an 80% sample water content), except for decabromodiphenyl ethane (DBDPE) (0.6ngg(-1) dry weight, 0.12ngg(-1) wet weight). The accuracy of the method was evaluated with three different types of spiked mollusk species using surrogate standards and standard addition over the extract for quantification and the recoveries were in the 70-120% range, except for bis(2-ethylhexyl)-3,4,5,6-tetrabromo-phthalate (DEHTBP) in clam (Ruditapes philippinarum) samples (46% recovery). Moreover, the method was successfully validated with standard reference materials (SRMs) of salmon and mussel tissues for BDEs. Finally, the method was applied to the determination of HFRs in different kind of freeze-dried mollusks: mussel (Mytilus galloprovincialis), cockle (Cerastoderma edule) and clam (R. philippinarum). Raft cultured mussels showed the highest concentrations of HFRs (up to 0.8ngg(-1) wet weight of BDE-209).

Determination of Δ9-tetrahydrocannabinol and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol in water samples by solid-phase microextraction with on-fiber derivatization and gas chromatography–mass spectrometry

A new method for the determination of two cannabinoids, Δ9-tetrahydrocannabinol (THC) and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH), in wastewater samples is proposed using solid-phase microextraction (SPME) as extraction technique and gas chromatography coupled to mass spectrometry (GC-MS) as determination technique. Several parameters involved in SPME extraction were studied and optimized (time, temperature, volume, pH and ionic strength of sample, and type of fiber). Moreover two derivatization reagents, N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) and N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide (MTBSTFA), were studied in depth, providing MSTFA the best results. The use of internal standard calibration (with their corresponding deuterated analogs) allows avoiding standard addition calibration for the quantification of samples. Under optimal conditions, limits of detection at low nanograms per liter were achieved (1.0 and 2.5 ng L⁻¹ for THC and THCCOOH respectively). Precision (RSD<15%) and trueness (92-112% relative recovery) were also satisfactory. Analysis of several samples from a wastewater treatment plant (WWTP) shows the presence of cannabinoids at notable concentrations in raw wastewater (12-35 ng L⁻¹ for THC and 50-153 ng L⁻¹ for THCCOOH) and an incomplete removal, which translates into their detection in the receiving river.

Ion-pair sorptive extraction of perfluorinated compounds from water with low-cost polymeric materials: Polyethersulfone vs polydimethylsiloxane

A method for the determination of seven perfluorinated carboxylic acids and perfluorooctane sulphonate (PFOS) in aqueous samples using low-cost polymeric sorptive extraction as sample preparation technique, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) determination has been developed and validated. Simplicity of the analytical procedure, low volume of solvent and sample required, low global price and a good selectivity providing cleaner extracts are the main advantages of this extraction technique. Polydimethylsiloxane (PDMS) and polyethersulfone (PES) materials were evaluated and compared to achieve the best extraction efficiencies. Hence, different variables have been optimized, viz.: sample pH, concentration of an ion-pairing agent (tetrabutylammonium), ionic strength, sample volume, extraction time, desorption solvent volume, desorption time and the need for auxiliary desorption techniques (sonication). Overall, PES leaded to a better sensitivity than PDMS, particularly for the most polar compounds, reaching detection limits (LODs) in the 0.2-20 ng L(-1) range. The precision of the method, expressed as relative standard deviation (RSD), was lower than 16%. Finally, the PES material was employed for the analysis of sea, sewage and fresh water samples. Perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA) were detected in all the analyzed influent samples reaching levels of up to 401 ng L(-1). In surface water, perfluorohexanoic acid (PFHxA) exhibited the highest concentrations, up to 137 ng L(-1).

Application of polydimethylsiloxane rod extraction to the determination of sixteen halogenated flame retardants in water samples

An extraction and preconcentration procedure for the determination in water samples of several halogenated flame retardants (FRs), nine brominated diphenyls ethers (BDEs) and seven non-BDE FRs, was developed and validated. The optimised procedure is based on polydimethylsiloxane (PDMS) rods as sorptive extraction material, followed by liquid desorption and gas chromatography coupled to negative chemical ionisation-mass spectrometry (GC-NCI-MS) determination, rendering an efficient and inexpensive method. The final optimised protocol consists of overnight extraction of 100mL of sample solutions containing 40% MeOH and 4% NaCl, followed by a 15-min sonication-assisted desorption with 300 μL of ethyl acetate, solvent evaporation and GC-NCI-MS analysis. Under these conditions, extraction efficiencies in the 9 to 70% range were obtained, leading to enrichment factors between 108 and 840, detection limits in the range from 0.4 to 10 ng L(-1)and RSD values in the 2-23% range. After method validation, different real water samples, including river, ria, sea, landfill leachate, influent and effluent wastewater from an urban sewage treatment plant (STP) and effluent wastewater from a textile industry, were analysed. BDE-47, BDE-99, BDE-100 and BDE-197 were detected in wastewater and landfill leachate samples at concentration levels up to 2887 ng L(-1). Among the non-BDE FRs, bis (2-ethylhexyl)-3,4,5,6-tetrabromo-phthalate (DEHTBP) was detected in surface water samples (sea, river and ria) between 1.3 and 2.2 ng L(-1) and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) in the landfill leachate (64 ng L(-1)).

Solid-phase extraction of perfluoroalkylated compounds from sea water

This study describes an in-depth investigation of the parameters involved in the solid-phase extraction performance of perfluoroalkylated compounds (seven carboxylates and one sulfonate), particularly with sea water samples. The two most popular sorbents, Oasis WAX and Oasis HLB, were considered and it was observed that the high ionic strength of sea water may impair solid-phase extraction recoveries. In the final protocol, Oasis HLB cartridges were selected, incorporating a 10% methanol clean-up step before elution with methanol, since less matrix effects were obtained. The proposed method allows successful recoveries, higher than 71%, and relative standard deviations lower than 20%. It also provides excellent limits of detection values between 0.01 and 0.21 ng/L. Finally, the method was applied to fresh and sea water samples, where several perfluoroalkylated compounds were found at concentrations ranging between 0.16 and 64 ng/L. In the case of perfluorooctane sulfonate, recently included in the Water Frame Directive, its concentration reached the highest values among the perfluoroalkylated compounds measured (64 ng/L in river samples).

Bioaccumulation of UV filters in Mytilus galloprovincialis mussel

In this study the bioaccumulation kinetics of organic UV filters, such as 4-MBC, BP-3, BP-4, OC and OD-PABA in wild Mytilus galloprovincialis mussels was investigated. The uptake and accumulation of waterborne 4-MBC, BP-4 and OC was very rapid, and after only 24xa0h of exposure to 1xa0μgxa0L-1, the tissular concentrations were 418, 263 and 327xa0μgxa0kg-1d.w., respectively. The kinetics of bioaccumulation of BP-4 and OC significantly fitted to an asymptotic model with BCF values of 905xa0Lxa0kg-1 and 2210xa0Lxa0kg-1, respectively. Measured bioaccumulation of the hydrophilic chemical BP-4 was much higher than predicted by Kow-based bioconcentration models, which would lead to a marked underestimation of actual risk. On the other hand, the patterns of uptake found for BP-3 and OD-PABA suggest biotransformation ability of mussels for these two chemicals.

Matrix solid-phase dispersion combined to liquid chromatography–tandem mass spectrometry for the determination of paraben preservatives in mollusks

A method for the extraction and determination of seven parabens, esters of 4-hydroxybenzoic acid, widely used as preservatives in personal care products, pharmaceuticals, etc., and two chlorinated derivatives (mono- and di-chloro methyl paraben) from mollusk samples was developed by combining matrix solid-phase dispersion (MSPD) and liquid chromatography-tandem mass spectrometry. MSPD parameters, such as solvent, solid support and clean-up sorbent, were optimized. Besides, since blank problems were observed for some parabens, these were investigated and blanks were tackled by precleaning all sorbents prior to use. Under final conditions, 0.5g of freeze-dried mollusk were dispersed with 1.2g of silica and packed into a cartridge containing 3g of C18, as on-line clean-up sorbent. This cartridge was eluted with 10mL of acetonitrile, evaporated and reconstituted in methanol for analysis. In the validation stage, successful linearity (R(2)>0.999), recoveries (between 71 and 117% for most analytes), precision (RSD lower than 21%) and limits of detection and quantification (LOD and LOQ, lower than 0.4 and 1.4ngg(-1) dry weight respectively) levels were achieved. Finally, the new methodology was applied to mussel, clam and cockle samples. Methyl paraben was above the LOQ in five of the six samples (not found in one clam sample) at concentrations up to 7ngg(-1) dry weight. Ethyl paraben was found above the LOQ in mussel and cockle samples at a concentration level around 0.3ngg(-1). n-Propyl paraben was only above the LOQ in one mussel sample.